The present invention relates to a device for connecting a wiper blade for windows of motor vehicles to a driven wiper arm guided on a motor vehicle.
In wiper blades the support element for the entire field swept by the wiper blade is intended to assure the most uniform possible distribution of the wiper blade contact pressure against the window that originates at the wiper arm. By a suitable curvature of the unstressed support element--that is, when the wiper blade is not contacting the window--the ends of the wiper strip, pressed completely onto the window during wiper blade operation, are stressed by the then-stressed support element toward the window, even if the radii of curvature of spherically curved vehicle windows change for every wiper blade position. The curvature of the wiper blade must accordingly be somewhat greater than the greatest curvature measured in the field to be wiped in the window in question. Thus the support element replaces the complicated support bracket construction with two spring rails, disposed in the wiper strip, of the kind used in the conventional wiper blades discussed above. A wiper blade of this kind should be capable of being connected in captive fashion to the wiper arm in a simple way and equally simply removed from it again.
The invention takes this connecting device as its point of departure. In a known connecting device of this type (German Published, Non-Examined Patent Application DE-OS 23 44 876), the support element is made from a plastic. The two lateral connection projections are formed directly onto the support element and therefore comprise the same material as the support element. In wiper blade operation, especially high demands for elasticity are made of the support element, because it is intended to distribute the contact force, acting on the wiper blade via the wiper arm and oriented toward the window, as uniformly as possible over the entire length of the wiper blade, specifically even if the radii of curvature of the windows, which as a rule are spherically curved, change constantly in the region of the window to be swept by the wiper blade. Conversely, stringent demands for wear resistance together with good sliding properties are made of the projections. As a result, in designing the known wiper blade, or the support element belonging to it, compromises have to be made that stand in the way of an optimal way of meeting both demands.